A Central City assistant police forensic investigator. Moments after an explosion at the S.T.A.R. Labs particle accelerator, Barry is struck by lightning in his laboratory and doused by chemicals affected by the accident. When he awakens from a nine-month coma, he has superhuman speed.[7] In September 2013, Grant Gustin was cast in the titular role.[7] Andy Mientus, who would eventually be cast as Hartley Rathaway, also auditioned for the role.[8] Gustin began researching the character during the audition process, and reading as many comics as possible. Gustin primarily focused on The New 52 series of comics, because he knew it would be difficult to read everything and he felt the New 52 was the closest to the show's "look and feel".[9]

A highly intelligent bioengineering expert, Caitlin believed her fiancé, Ronnie Raymond,[12] was killed during the particle accelerator explosion at S.T.A.R. Labs,[13]until he returned part way through first season. Ronnie and Caitlin get married in the first season finale, "Fast Enough".[14]

The mind and money behind Central City's S.T.A.R. Labs Particle Accelerator, Wells becomes a pariah after the lab explodes.[16] Mentoring Barry to get faster, he is eventually revealed to be the Reverse-Flash, Eobard Thawne (Matt Letscher), a descendant of Eddie from the future with a grudge against the Flash. Thawne killed the real Wells and stole his identity.[17] In subsequent seasons, Cavanagh portrays various alternate reality doppelgängers of Wells. These include the sarcastic but brilliant "Harry", who along with his daughter Jesse hails from Earth-2, and his Earth-19 counterpart, the sci-fi novelist "H.R.".

The son of Joe and brother of Iris, born without their knowledge after his mother left Central City.[19] The producers disliked the introduction of relatives of characters that were never previously mentioned, feeling it was "weird", and opted instead to introduce Wally as unknown even to his relatives. They also chose to make him Iris' brother, a departure from the comics where he was her nephew.[19] Speaking on Lonsdale's casting, Kreisberg explained that "Just like when we met Grant [Gustin] for the first time, we instantly knew Keiynan embodied all the heart and courage of a hero."[20] After Flashpoint, Wally eventually gets speed powers from Doctor Alchemy and becomes Kid Flash.[21]